Chair, especially dentist&#39;s chair



July 11. 19 A. G. svARD 3,330,595

CHAiR. ESPECIALLY DENTIST'S CHAIR Filed Jan, 20, 1966 2 Sheets-Sheet 1INVENTOR. /4L F Gfales 514420 Y r JM July 11, 1967 A. G. svARD 3,330,595

CHAIR. ESPECIALLY DENTISTS CHAIR Filed Jan. 20, 1966 2 Sheets-Sheet 2 IN V EN TOR. 44 F Gib/e6 5 law By r iii 1) United States Patent 3,330,595CHAIR, ESPECIALLY DENTISTS CHAIR Alf Georg Svtird, Matrosvagen 6,Saltsjobaden, Sweden Filed Jan. 20, 1966, Ser. No. 521,939 Claimspriority, applicatiorzssweden, Jan. 25, 1965,

7 Claims. (Cl. 297--71) Existing dentists chairs suffer from a pluralityof inconveniences. Chairs in which the patient assumes a sitting posturecompel the dentist to work standing and usually in an uncomfortable andfatiguing posture. In a type of chairs, the so called relaxation chairs,the conventional foot-rest is replaced by a projection which makes arelatively small angle with the horizontal. During the treatment thepatient places his legs on this projection. The chair is uncomfortablefor the patient to sit down because the seat has to be taken from theside of the chair which for many patients requires help from the dentistor nurse. Certain stages of dental treatment require inspection of theoral cavity directly from the front in which case the oral cavity islocated too far from the dentist. In order to provide for a betterworking posture for the dentist, the so called contour chair has beenconstructed which comprises a horizontal front portion and an even andcontinuous back portion and in which the position of the head of thepatient is varied by means of cushions. This chair has the same drawbackas the previously mentioned chair and involves additional problems. Forinstance, the backrest on being turned downwards draws the clothes ofthe patient, and the chair does not suit patients of different heights.

The object of this invention is to eliminate the above inconveniencesand in addition to provide a construction of a dentists or other chairwhich in each position allows the patient to assume an anatomicallycorrect posture. Such posture can be maintained during continuous changefrom sitting to lying position and vice versa.

In its broadest aspect the invention is characterized in that a legsupport appertaining to the chair comprises a thigh support and a shanksupport making an angle with each other and articulated to each otherand to a seat in such a manner that the angle between the thigh supportand the shank support is increased when the shank support is moved fromsitting to lying position. The term sitting position refers to aposition in which the upper body of the patient is substantially uprightor slightly rearwardly inclined, whereas the term lying position refersto a position in which the upper body of the patient is substantiallyhorizontal.

Due to the fact that the angle between the thigh support and the shanksupport is increased when the patient is about to assume a lying posturethe patient is compelled during this movement to straighten his legs andthereby to compensate for the displacement of the centre of gravityoccurring during this movement. Consequently, in this respect the chairadapts itself to the natural move ment which the legs of the human bodytend to make on changing from sitting'to lying posture.

To obtain a comfortable sitting position it is suitable that the thighsupport in this position is parallel to or on a level with the seat andin lying position makes an angle with the seat so that the thighs of thelying patient, with the backrest turned downwards, make an angle withthe upper body of the patient. Such posture is felt comfortable andcalming.

In order to ensure that the leg support automatically assumes a properposition on changing of the chair from sitting to lying position, thehigh support and the shank Ice support may be substantially in the formof a linkage comprising two links having a common pivot, one end of thelinkage being articulated to the seat at a place comparatively close tothe backrest and the other end being articulated, by means of anadditional link, to the seat at or near the front edge thereof, To thesame end, said additional link which in the sitting position connectsthe lower end of the shank support with the seat may in said positionmake an acute angle with the shank support which angle is increased whenthe shank support is swung upwards from sitting to lying position.

In order to have the backrest, too, anatomically adaptable to the backof the patient it may comprise an upper section forming a support forthe shoulders of the patient and a lower section serving as a supportfor the small of the back of the patient, said sections beingdisplaceable relative to each other for adaptation to patients havingdifferent lengths of the back.

Further, the lower portion of the shank support may be narrower than theupper position so as to make it easier for the patient to sit down onthe chair and to allow the dentist to assume a comfortable posture whentreating the patient directly from the front.

A further improvement consists in that the backrest is provided witharmrests preventing the arms of the patient from falling when thebackrest is turned backward.

The invention is described more closely hereinbelow with reference to anembodiment thereof illustrated in the annexed drawing. FIG. 1 is adiagrammatic view of the linkage considered to be formed by the parts ofa chair according to the invention. FIG. 2 is a more detailed lateralelevation and FIG. 3 a front elevation of the chair.

In the linkage illustrated in FIG, 1 reference numeral 10 corresponds tothe seat of the chair, numeral 12 to a thigh support and numeral 14 to ashank support which via a hinge 16 is connected to the thigh support.The thigh support 12 is articulated to the seat at a pivot 18, and thelower end of the shank support is by means of an additional link 20articulated to the front edge of the seat. The common pivot of the links14 and 20 is indicated at 22 in FIG. 1, whereas the pivot at the frontedge of the seat is indicated at 24. The pivot 18 is located near therear edge of the seat to which a pivoted backrest 26 is alsoarticulated.

In the sitting position shown by full lines in FIG. 1 the links 12, 14make an angle v with each other corresponding to a comfortable sittingposture of the patient with his thighs resting on the thigh support andhis shanks resting on the shank support. If now the lower end of theshank support is swung upwards for changing the sitting posture of thepatient to a lying position the angle v will be increased and in thelying position amounts to v The links are illustrated in lying positionsby chaindotted lines. At the same time the thigh support 12 is swungupwards from a substantially horizontal position to a position in whichit makes an angle u with the seat 10. Consequently, if the patient islying down as the backrest 26 is turned backward about its pivot 28 hewill straighten his legs as compared with the sitting posture andcorresponding to the increase of the angle v to v thereby compensatingfor the rearward displacement of the centre of gravity which otherwisewould occur due to the backward movement of the patients back. In thelying posture the thighs of the patient are slightly raisedcorresponding to the angle u, resulting in a comfortable lying posture.

The backrest comprises an upper section 30 forming a support for theshoulders of the patient and a lower section 32 serving as a support forthe small of the back of the patient. The sections are displaceablerelative to each other for adaptation to patients having differentlengths of the back. The upper section 30 is interconnected with thelower section 32 by having one of the sections, for instance, the lowerone, provided at its lateral edges with a guide rail 34 which isslidably engaged by a guide bar 36 at either edge of the upper section30. In order to provide for an improved support for the small of theback of the patient along a greater area, the lower section 32 has anupwardly projecting central portion 38, which fits a central recess 40in the upper section 30 when the sections 30 and 32 are together.

As shown in FIG. 3 the lower portion of the shank support is narrowerthan the upper portion so as to provide room for the feet of the patientabout to sit down on the chair and for the dentist treating the patientfrom the front. Consequently, the patient can place himself in front ofthe chair with one foot on either side of the lower narrow portion ofthe shank support and then conveniently sit down on the chair.

Provided on either side of the backrest are forearm supports 42preventing the arms of the patient from falling when the backrest isturned backward. Provided at the upper part of the backrest is a support44 for the nape of the neck of the patient and an armrest 46 for thedentist. The nape support can be turned about a pivot 48 which maycomprise means for locking the nape support in adjusted position. 1

The various adjusting movements for the various parts of the chair maybe performed manually, but are considerably facilitated by the use ofhydraulic jacks. FIG. 3 illustrates a hydraulic cylinder 50 secured tothe lower section 32 of the backrest, and an associated piston 52 whichis connected to the upper section 30. This construction allows automaticadjustment of the upper section of the backrest relative to the lowersection. For turning the backrest there is provided a hydraulic cylinder54, FIG. 2, the piston 56 which is articulated to a crank arm 58 whichis rigidly connected to the lower end of the backrest and consequentlyupon movement of the piston in the cylinder is turned about the pivot 28of the backrest. A further hydraulic cylinder 60 having a piston 62 isprovided for turning the shank support upwards and downwards. Thedownwards movement of the backrest and the swinging movements of the legsupports may be coordinated such that the leg rests are turned up to theposition shown by chain-dotted lines at the same time the backrest isturned backward to lying position. These movements are preferablycontrolled in such a manner that the legs of the patient will besuccessively straightened to the position v in FIG. 1 while the upperbody of the patient is being lowered. This is an anatomically correctmanner that prevents material changes in the position of the centre ofgravity of the patient during this movement. Corresponding conditionsapply when the backrest is to be turned upwards and the patient is toassume a sitting posture.

The chair may be constructed, in a manner known per se, to be lifted andlowered on a foot 64 and may also comprise arm rests 66 to be used inthe sitting position.

The chair may be constructed in a manner to permit variation of theangle v by varying the length of the link 20, such as by making thislink of two parts, one of which has secured to it a hydraulic cylinder68 while the other part is connected with a piston 70 displaceable inthe cylinder, as indicated in FIG. 1. The arrangement may be such thatthe links 12, 14 can be adjusted in line with each other or at anydesired suitable angle.

The invention is not limited to the illustrated embodiment which is onlyan example. The upper section of the backrest may be detachable andexchangable so that backrest sections of different lengths may beinserted according to the length of the back of the patient. Instead ofhydraulic operation, pneumatic cylinders may be employed or evenmanually operable cranks acting on screw and nut devices. Variouscombinations of such operating devices are conceivable.

What I claim is:

1. A chair comprising a seat, a backrest pivoted to the seat, a thighsupport articulated at a first point to the seat, a shank supportarticulated to the thigh support, said supports forming an angle betweenone another, and connecting means to actuate the lower end of the shanksupport for swinging it from a sitting position to a lying position,said means comprising a link having one end pivoted at a second point tothe lower end of the shank support and its other end pivoted at a thirdpoint to the seat, the length of said link plus the straight linedistance between said first and third points being greater than thestraight line distance between said first and second points when theshank support is in said sitting position so as to augment said angle asthe shank support is moved from a position for sitting in the chair to aposition for lying therein.

2. A chair as claimed in claim 1, characterized in that the thighsupport in sitting position is parallel to or on a level with the seatand in lying position makes an angle with the seat so that the thighs ofthe lying patient, while the backrest is turned downwards, make an anglewith the upper body of the patient.

3. A chair as claimed in claim 1, characterized in that the thighsupport and the shank support are substantially in the form of a linkagecomprising two links having a common pivot, one end of the linkage beingarticulated to the seat at a place comparatively close to the backrestand the other end being articulated, by means of an additional link, tothe seat at or near the front edge thereof.

4. A chair comprising a seat, a backrest pivoted to the seat, a thighsupport articulated to the seat, a shank support articulated to thethigh support, said supports forming an angle between one another, andconnecting means between the shank support and the thigh supportproviding mutual guidance therebetween, the backrest comprising an uppersection forming a support for the shoulders of the patient and a lowersection serving as a support for the small of the back of the patient,said sections being displaceable relative to each other for adaptationto patients having different lengths of the back.

5. A chair as claimed in claim 4, characterized in that the lowersection of the backrest has an upwardly projecting central portion andthat the upper section has a corresponding recess.

6. A chair comprising a seat, a backrest pivoted to the seat, a thighsupport articulated to the seat, a shank support articulated to thethigh support, said supports forming an angle between one another, andconnecting means between the shank support and the thigh supportproviding mutual guidance therebetween, said shank support comprising alower portion and an upper portion, the lower portion of the shanksupport being narrower than the upper portion so as to provide room forthe feet of the patient about to sit down on the chair and for thedentist treating the patient from the front.

7. A chair as claimed in claim 1, characterized in that the length ofsaid link is variable.

References Cited UNITED STATES PATENTS 2,617,118 11/1952 Lorenz 29783 X2,714,922 8/ 1955 McKibbon et al. 297--83 2,753,920 7/1956 Ranger 297833,147,038 9/1964 Barabas 297316 X 3,191,990 6/1965 Rugg et al. 297833,222,105 12/1965 Cross 29783 X 3,235,307 2/1966 Knabusch et al. 297-69X FOREIGN PATENTS 97,308 11/1963 Denmark.

DAVID J. WILLIAMOWSKY, Primary Examiner.

JAMES T. MCCALL, Examiner.

1. A CHAIR COMPRISING A SEAT, A BACKREST PIVOTED TO THE SEAT, A THIGHSUPPORT ARTICULATED AT A FIRST POINT TO THE SEAT, A SHANK SUPPORTARTICULATED TO THE THIGH SUPPORT, SAID SUPPORTS FORMING AN ANGLE BETWEENONE ANOTHER, AND CONNECTING MEANS TO ACTUATE THE LOWER END OF THE SHANKSUPPORT FOR SWINGING IT FROM A SITTING POSITION TO A LYING POSITION,SAID MEANS COMPRISING A LINK HAVING ONE END PIVOTED AT A SECOND POINT TOTHE LOWER END OF THE SHANK SUPPORT AND ITS OTHER END PIVOTED AT A THIRDPOINT TO THE SEAT, THE LENGTH OF SAID LINK PLUS THE STRAIGHT LINEDISTANCE BETWEEN SAID FIRST AND THIRD POINTS BEING GREATER THAN THESTRAIGHT LINE DISTANCE BETWEEN SAID FIRST AND SECOND POINTS WHEN THESHANK SUPPORT IS IN SAID SITTING POSITION SO AS TO AUGMENT SAID ANGLE ASTHE SHANK SUPPORT IS MOVED FROM A POSITION FOR SITTING IN THE CHAIR TO APOSITION FOR LYING THEREIN.